I am a firm believer in the KISS principle...Keep it simple s.....
If you want to design a new "no guns-no money" type card, you need to make it one that can be read and understood in one glance
You might consider a visual on one side, like, the gun in a circle with a slash, and large bold "=" and then a large $ in a circle with a slash.
On the back side you could say something like: "If a law abiding citizen cannot carry for their own, and your, security here, then only criminals will"
That might even be too much....Keep it Simple